Water Filtration Solutions
Olefins Unit Wastewater Treatment water treatment system in operation
Application 07

Olefins Unit Wastewater Treatment

Purpose-built treatment for ethylene cracker process water

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OverviewProcess & ParametersChallenges & SolutionsPerformanceFiltrationSchematicSpecificationsLayoutDeliverables
Process Overview

What this application solves

Ethylene (olefins) plants generate process water from quench towers, dilution-steam systems and the caustic wash that removes CO₂ and H₂S. These streams carry dissolved and free hydrocarbons, oxygenates (aldehydes, ketones), polymer/'green oil', and sulfidic spent caustic — a demanding combination.

WFS integrates oil removal, dissolved-gas and oxygenate management, spent caustic pre-treatment and biological polishing into a train tailored to the cracker's feed slate and configuration.

Application Parameters

Typical influent characteristics

ParameterTypical range
COD1,000 – 20,000 mg/L
Hydrocarbons100 – 5,000 mg/L
Sulfidesup to 20,000 mg/L
Oxygenatesmoderate – high
Polymer / green oilfouling

These ranges frame the design basis. WFS confirms the exact values for your site through laboratory characterization and 24-hour composite sampling, capturing variability across normal, upset and turnaround operation before any equipment is sized.

COD
1,000 – 20,000 mg/L
Hydrocarbons
100 – 5,000 mg/L
Sulfides
up to 20,000 mg/L
Oxygenates
moderate – high
Challenges & Solutions

The problems — and how WFS solves them

Challenges faced
  • Polymeric 'green oil' fouling of equipment
  • Sulfidic spent caustic toxicity & odor
  • High and variable COD / hydrocarbon loads
  • Oxygenates that are hard to remove
  • Tight integration with cracker operation
Solutions needed
  • Dedicated spent caustic oxidation / neutralization
  • Multi-stage oil removal (separation + flotation)
  • Sour-water / dissolved-gas stripping
  • Biological treatment tuned for oxygenates
  • Tertiary filtration & carbon polishing
Performance Parameters

Targets the system is designed to meet

Performance parameterDesign target
Oil & Grease< 10 mg/L
COD removal> 90%
Sulfide< 1 mg/L
Effluentdischarge / reuse spec

Guaranteed, tested performance

Every WFS system is commissioned against a documented performance test. We design to the discharge consent, reuse specification or zero-liquid-discharge target — and verify it on site before handover, then sustain it through O&M.

Filtration Approach

Filtration approach & system required

The spent caustic and oily streams are pre-treated separately to their own best technology, then combined for biological polishing. This staged, segregate-then-combine strategy keeps the biology stable.

Anti-foulant management and easy-clean separation handle the green-oil tendency throughout the train.

Filtration system required
  • Spent caustic oxidation / neutralization unit
  • Oil-water separators & flotation packages
  • Sour-water / gas stripping column
  • Biological reactor (MBBR / MBR)
  • Tertiary filtration & activated carbon
Treatment Train

Modular process-train schematic

Treatment Train Schematic Influent Treated
  1. 1Stream Segregation
    Separate caustic / oily routing

    Treat each at best technology

  2. 2Spent Caustic
    Oxidation / neutralization

    Destroy sulfides, cut COD

  3. 3Oil Removal
    Separator + IGF/DAF

    Remove HC & green oil

  4. 4Stripping
    Sour-water / gas stripping

    Remove dissolved gases

  5. 5Biological
    MBBR / MBR

    Oxidize COD & oxygenates

  6. 6Polishing
    Filtration + GAC

    Final solids & organics

System Specifications

Indicative system specification

Capacity range
20 – 600 m³/h
Configuration
Basins + modular skids
Materials
SS316L, lined CS, FRP
Automation
Integrated with cracker DCS
Anti-fouling
Green-oil management
Codes
ASME, API, ISO, EHS
Plant Layout

Layout & general arrangement

Segregated inlet headers feed parallel pre-treatment blocks (caustic vs oily), which converge on common biological and polishing trains. The spent caustic block is a bunded hazardous area set apart from the rest.

Layout supports cracker turnaround tie-ins and provides clear access to flotation and biological units for cleaning.

Inlet ▸General Arrangement — Plot Plan▸ Outlet
  1. 01
    Stream Segregation
  2. 02
    Spent Caustic
  3. 03
    Oil Removal
  4. 04
    Stripping
  5. 05
    Biological
  6. 06
    Polishing
Utilities · Chemical Dosing · MCC / Control Room · Sludge Handling · Laboratory
Project Deliverables

What WFS delivers

  1. 1Stream-by-stream characterization & balance
  2. 2Integrated treatment design for the olefins complex
  3. 3Spent caustic & oil-removal package design
  4. 4Fabrication, delivery & construction
  5. 5DCS integration, E&I & commissioning
  6. 6Performance testing to discharge/reuse spec
  7. 7O&M contract & operator training
Delivery Model

From study to continuous O&M

  1. 01
    Study & Assess
  2. 02
    Characterize Water
  3. 03
    Custom Design
  4. 04
    Pilot & Trial
  5. 05
    Detailed Engineering
  6. 06
    Equipment Design
  7. 07
    Fabricate
  8. 08
    Deliver to Site
  9. 09
    Construct
  10. 10
    Electrical & Automation
  11. 11
    Continuous O&M

Discuss your olefins unit wastewater treatment project

Share your stream data and target specification — WFS will characterize the water and propose a custom train.

Request a Consultation
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